1. Field of the Invention
This invention relates to a magnetic recording and/or reproducing apparatus, and more particularly can be applied to, for example, editing of multichannel audio signals by utilizing a digital audio tape recorder.
2. Description of the Related Art
Conventionally, there has been known a digital audio tape recorder which is designed to record or reproduce high quality audio signals by recording or reproducing digital audio signals with a rotary drum.
In the digital audio tape recorder, as shown in FIG. 1, three types of formats recorded and reproduced with a sampling frequency of 32 kHz!, 44.1 kHz!, or 48 kHz! are provided. In a format of 32 kHz! sampling frequency, 2- or 4-channel audio signals can be recorded and reproduced by changing of the rotating speed of a rotary drum.
It is expected that the utility of such digital audio tape recorder can be improved if such recorder can record or reproduce an audio signal in or from multichannels.
In addition, in such case, if digital audio signal can be recorded or reproduced, an editing or mixing process can be performed by using one reel of magnetic tape, as required, so that the utility can be further improved.
A system has been proposed in which reproducing and recording magnetic heads are arranged on a rotary drum so that digital audio signals reproduced by the reproducing magnetic head is subject to an editing or mixing process, and then the processed signals are rerecorded by the succeeding recording magnetic head. Thus processing is referred to as a processing of write-after-read.
In this case, audio data for multichannels can be recorded or reproduced by time base compressing and multiplexing the multichannel audio data, whereby the write-after-read processing can be attained for multichannel audio data.
It is believed to be convenient if the multichannel digital audio tape recorder can also edit 2-channel audio signals as described in the above.
An apparatus, which can record and reproduce audio signal in or from multichannels and can perform write-after-read, is disclosed in U.S. patent application Ser. No. 912,226 filed Jul. 10, 1992.
However, there is a problem that the write-after-read processing can not be performed because the processing of time base compression and expansion takes time so that reproducing and recording audio data takes time, if the magnetic head for recording and reproducing is arranged as the case where audio data of two channels are respectively edited.
Furthermore, the reproduced audio data cannot be recorded on the original recording tracks. Consequently, the multichannel digital audio tape recorder suffers from a problem that write-after-read processing cannot be performed in a case where the number of channels is changable.
Also, in the format of the sampling frequency 44.1 kHz! and 48 kHz! similar to the case of the format of sampling frequency 32 kHz!, if 4-channel digital audio signal can be recorded or reproduced, audio signal having higher quality can be recorded or reproduced with 4-channel in comparison with the case of the format of sampling frequency 32 kHz!, so that the utility can be further improved.
In this case, it is considered to use the same method with the case of the format of sampling frequency 32 kHz! so as to record or produce 4-channel audio signal.
That is, it is considered that, in the 4-channel format of sampling frequency 32 kHz!, the speed for forming recording track and the processing speed of the signal processing system are doubled, and 4-channel audio signal is multiplexed, as a result 4-channel audio signal is recorded and reproduced.
In this method, the format of sampling frequency 48 kHz! can record or reproduce 4-channel audio signal. However, there is a problem that the format of sampling frequency 44.1 kHz! can not record or reproduce 4-channel audio signal.
That is, this type of the digital audio tape recorder performs interleave processing for input data in every cycle (hereinafter, referred to as "1 frame cycle") which forms a pair of recording tracks consisting of the plus and minus azimuth angles.
Because of this, regarding the digital audio signal, when the speed for processing magnetic tape driving system is doubled and the 4-channel digital audio signal is recorded and reproduced, it is required that the cycle forming a pair of recording tracks is kept to an integer multiple.
In this case, the speed for processing magnetic tape driving system is doubled so that the cycle forming recording tracks can be shown to be 15 msec!, and the format of sampling frequency 48 kHz! can be represented by the following formula: EQU 15 msec!.times.48 kHz!=720 sample/frame! (1)
Therefore, it can be recognized that the cycle forming a pair of recording tracks is kept to an integer multiple of sampling cycle of the audio data.
The format of sampling frequency 44.1 kHz! can be shown by the formula: EQU 15 msec!.times.44.1 kHz!=661.5 sample/frame! (2)
when its speed is doubled similar to the case of sampling frequency 48 kHz!.
Therefore, it can be recognized that the cycle forming a pair of recording tracks is not kept to an integer multiple of sampling cycle of the audio data.
There is a case where the cycle forming a pair of recording tracks is not an integer multiple of sampling cycle of audio data depending on the sampling frequency described above, and a problem occurs in which data is not completed.